US2582684A

US2582684A - Electron tube structure

Info

Publication number: US2582684A
Application number: US104198A
Authority: US
Inventors: Donald F Drieschman; Hubert H Eaves
Original assignee: Eitel Mccullough Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1949-07-12
Filing date: 1949-07-12
Publication date: 1952-01-15
Anticipated expiration: 1969-01-15

Description

1952 D. F. DRIESCHMAN EI'AL 2,582,68

ELECTRON TUBE STRUCTURE 2 SHEETS-SHEET 1 Filed July 12, 1949 H m 0 u W C w E M Huber? H Eaves ATTORNEY I Jan. 15, 1952 D. F. DRIESCHMAN EI'AL 2,532,684

ELECTRON TUBE STRUCTURE Filed July 12, 1949 2 SHEETS-SHEET g INVENTORS Dona/d E Drfiescbman Hubs/'7 /7. Eaves ATTORNEY Patented Jan. 1 5, 1952 v ELECTRON TUBE STRUCTUiRE Donald F. Drieschman, Los Altos, and Hubert H.

Eaves, Palo Alto, Calif., asslgnors to Eitel McCullough, Inc., San Bruno, Calif., a corporation of California Application is, 12, 1949, Serial No. 104,198

12 Claims. (Cl; 313-252) l Our invention relates to improvements in the construction of negative-grid type electron tubes. and more particularly, to power tetrodes.

It is among the objects of our invention to i provide an improved tetrode for transmitting application such as modulator service.

Another object is to provide an electron tube of rugged construction, capable of withstanding heavy shocks without displacement'of the 'electrodes.

A further object is to provide a tube with a simplified base structure and improved electrode supports.

A still further object is to provide an improved envelope construction and sealing arrangement for enclosing the electrodes.

The invention possesses other objects and features of advantage, some of which with the foregoing, will be set forth in the following description of our invention. It is to be understood that we do not limit ourselves to this disclosure of species of our invention, as we may adopt variant embodiments thereof within the scope of the claims.

' Referring to the drawings:

Figure 1 is a vertical sectional view of our tube; and

Figure2 is a bottom view of the same.

In terms of broad inclusion, our electron tube comprises an evacuated envelope containing concentric electrodes such as a cathode, anode and one or more grids, our improvements relating particularly to the envelope construction and the electrode supp ting and terminal structure. As embodied in a tetrode, the envelope preferably comprises two sections sealed together along a plane transverse to the tube axis, with the anode supported by the upper'section and the cathode, control grid and screen grid supported by the lower section. The anode supporting lead on the upper section is preferably coaxial with the envelope axis and terminal pins for the other electrodes are preferably arranged .on the lower section to lie in a circle about the envelope axis. In our improved tube the lower envelope section comprises a molded vitreous header in which the terminal pins and electrode supports are sealed, conductor means between the pins and supports being preferably sealed within the vitreous header. The cathode support is preferably sealed centrally of the header and the supports for the control grid and screen grid are preferably sealed in circular formation about the cathode support, the grid mounts being preferably of conical shape with legs connected to the respective supports.

The anode lead is preferably tubularand communicates with the interior of the envelope to also provide the exhaust tubulation for the tube.

In greater detail and referring to the drawings, our improved electron tube, illustrated as a tetrode, comprises an envelope having an upper section 2 and a lower section 3. The upper section comprises acup-shaped blank 4 of a vitreous material such as glass having sealed to its lower edge a metal ring 6 provided with an outtumed flange 1. The lower section 3 comprises a vitreous header 9 forming the bottom wall of the envelope and has sealed along its periphery a metal ring II with an outtumed flange l2 registering with flange l of the upper section. Header 8 is preferably molded in the desired shape, as by melting powdered glass in a graphite mold. By such molded glass technique the'vari'ous metal parts hereinafter described may -readi1y be sealed in place during the molding operation. After the tube has been assembled the envelope sections are sealed together by a braze I3 about the periphery offlanges I and I2. V

In our tube the electrodes are of concentric cylindrical construction comprising a cathode ll, control grid l6, screen grid l1 and anode l8. The cup-shaped metal anode I 8 is supported from the upper envelope section 2 by a lead I! extending coaxially with the axis of the tube. This lead is hollow and serves the dual function of providing a conductor for the anode and an exhaust tubulation for the envelope. Tubular body H- of the lead is sealed to the upper portion of glass blank 4 and has a suitable fitting 22 at its lower end for fastening to the anode l8. 4 metallic extension 23 of the lead provides a connection to the exhaust system and, after evacuation of the envelope, is pinched off by' compressing the walls of the tubing together at tip 24. Slots 26 in the lead serve to retard heat flow from the anode to the glass seal. This improved anode lead structure removes the complications usually occurring when .an exhaust tubulation is arranged at the base portion of the tube. In our tube the absence of such an exhaust tubulation at the base materially simplifies the header structure.

The cathode I4, control grid l6 and screen grid I! are all mounted .on the lower envelope section 3 so that these electrodes .may be accurately assembled and aligned prior to the putting on of the upper half of the envelope. Cathode It comprises a cylinder of metal such as nickel, preferably cup-shaped, having an electron emissive coating such as the barium-strontium oxide mixture commonly used for that purpose. The

preferably cup-shaped sealed centrally in the header 8, this support being I with its lower portions embedded directly in the glass of the header. The flange of support 21 carries a sleeve 28 which in turn is connected to the cathode by an interposed sleeve 29. This latter sleeve is of thin metal having poor heat conductivity so as to thermally isolatethe cathode from the header structure. A metal rod 30 connected to the lower end of support 21 preferably projects out through the bottom of header 8 for the purpose of carrying heat out from the cathode supporting structure. This center rod may be used as a.

cathode terminal, but in our preferred tube construction is used merely as a cooling pin.

Cathode i4 is heated by a suitable heater 3| mounted within the cathode cylinder. This heater is preferably a coil of insulated tungsten wire lying against the inner wall of the cathode,

- connected: at one end to the cathode cylinder and at the other end to "a central lead 32. An

- end plate 33 closing the lower end of the cathode cylinder serves to conserve heat and is insulated from the lead 32 by an insulator bushing 34. Layers of corrugated sheets 36 at the top provide additional heat shielding and are preferably of a metal such as zirconium having gettering or gas-absorbing properties, the upper end of the cathode being preferably recessed to retain these disks.

Control grid l6 and screen grid I! which surround the cathode are preferably of the cage type, fabricated of suitable wire, and are supported at their lower ends from the header structure. The control grid supports 31, say three in number, are arranged in a circle about the cathode support. These supports are sealed in the header and project upwardly into the envelope to carry the control grid mount 38, the latter being preferably conical in shape and having three legs connected to outturned ends of the supports 31. In a like manner a plurality of screen grid supports 39 are sealed in the header in a larger circle surrounding the cathode support and spaced alternately with respect to the control grid supports; The conical mount 4| for the screen grid has legs connected to the supports 39,

' which legs lie between those of the control grid mount. This structure provides arugged mounting for the grids and reduces the capacitance effects between the grid supports.

Four

terminal pins

42, 43, 44 and 45 are sealed in the header to project downwardly frorr he envelope and are arranged ,in a circle abou. he tube axis, the upper ends of these pins being embedded in the glass of the header. The interconnections between the terminal. pins .and electrode supports are preferably sealed wholly within the glass of the header to further enhance the compactnessand ruggedness of the base structure. Thus the cathode pin 42 is connected to the rod 30 by a strap 46, the control grid pin 43 is connected to one of the supports 31 by a strap 41, and the'screen grid pin 44 is connected-to one of the supports 39 by a strap 48, which straps are embedded in the glass of the header. A post 49 connected to the header pin 45 projects upwardly within the envelope to support the outtumed end center rod 32, the latter extendin through a slot' Sl in cathode supporting sleeve 28. The various terminal pins and electrode supports which are sealed in the header are preferably molded directly to the glass when the header is formed in the mold. For this purpose the graphite mold is shaped to hold the ring u and other metal parts in proper position. Powdered glass is then poured in the mold and all .is brought up to the melting point of the glass maining electrodes on the header section, the

two sections of the envelope are fitted together and brazed at It along the abutting flanges.

We claim:

1. An electron tube comprising an envelope having amolded vitreous header at the lower end, concentric electrodes in the envelope including a cathode and grid, a support for the cathode sealed centrally in the header and projecting upwardly into the envelope, and supports for the grid sealed in the header in circular formation about the cathode support and pro- Jecting upwardly into the envelope, a conical mount for the'grid having diverging end portions connected to said grid supports, terminal pins for the electrodes sealed in the header and projecting downwardly from the envelope, and means connecting the pins to the respective electrode supports.

2. An electron tube comprising an envelope having a molded vitreous header at the lower end, concentric electrodes in the envelope including a cathode and control grid and screen grid, a support for the cathode sealed centrally in the header and projecting upwardly into the envelope, supports for the control grid and screen grid sealed in the header in circular formation about the cathode support and projecting upwardly. into the envelope, the circle defined by the screen grid supports being larger than that of the control grid supports, terminal pins for the electrodes sealed in the header and projecting downwardly from the envelope, and means connecting the pins to the respective electrode supports.-

3. An electron tube comprising an envelope having a molded vitreous header at the lower end, concentric electrodes in the envelope including a cathode and control grid and screen grid, a support for the cathode sealed centrally control grid supports, a conical mount for the control grid having diverging end portions connected to the control grid supports, a conical mount for the screen grid having diverging end portions connected to the screen grid supports. terminal pins for the electrodes sealed in the header and projectingdownwardly from the envelope, and means connecting the pins to the respective electrode supports.

4. An electron tube comprising an envelope having a molded vitreous header at the lower end, concentric electrodes in the envelope including a cathode, a support for the cathode comprising a cup having its lower portion sealed centrally in the header, said cup penetrating only partially into the header, and a sleeve connecting the cathode to the flange of said cup.

5. An electron tube comprising an envelope having a molded vitreous header at the lower end.

concentric electrodes in the envelope including a cathode and grid, a support for the cathode comprising a cup having its lower portions sealed centrally in the header, a sleeve connecting the cathode to the flange of said cup, supports for the grid sealed in the header in circular formation about the cathode support and projecting upwardly into the envelope, and a conical mount for the grid having legs connected to said grid supports.

6. An electron tube comprising an envelope having a molded vitreous header at the lower end, concentric electrodes in the envelope including a cathode and control grid and screen grid, a support for the cathode comprising a cup having its lower portion sealed centrally in the header, a sleeve connecting the cathode to the flange of said cup, supports for the control grid and screen grid sealed in the header in circular formation about the cathode support and projecting upwardly into the envelope, a conical mount for the control grid having legs connected to the control grid supports, and a conical mount for the screen grid having legs connected to the screen grid supports.

7. An electron tube comprising an envelope having upper and lower sections, the lower section having a molded vitreous header forming the bottom wall of the envelope, concentric electrodes in the envelope including an anode and cathode and grid, terminal pins and supports for the cathode and grid sealed in the header, and a lead for the anode sealed to the upper envelope section, the anode lead being coaxial with the envelope axis and said cathode and grid terminal pins being located in the circle about said axis,

said supports for the grid being located in a circle of different diameter than that of the terminal pins.

8. An electron tube comprising an envelope having a vitreous header at the lower end, concircle defined by the screen grid supports is the largest.

9. An electron tube comprising an envelope having a vitreous upper portion, concentric electrodes in the envelope including an anode, and a tubular metallic lead extending coaxially of the electrodes through the envelope for supporting the anode, the vitreous upper portion of the envelope being fused to the side walls of the tubular anode lead intermediate the ends of said lead, the lead providing a conductor for the anode and also communicating with the interior of the envelope to provide an exhaust tubulation, the outer end of the lead having its side walls compressed together to close the tubulation.

10. An electron tube comprising an envelope having a vitreous upper portion, concentric electrodes in the envelope including an anode, a tubular metallic lead extending coaxially of the electrodes through the enve the anode, the vitreous upper por velope being fused to the side walls of the tubular anode lead intermediate the ends of said lead, the lead providing a conductor for the anode and also communicating with the interior of the envelope to provide an exhaust tubulation, the outer end of the lead having its side walls compressed together to close the tubulation, a cap across the upper end of the anode, and means connecting the anode cap to the inner end of said lead.

11. An electron tube comprising an envelope having upper and lower sections joined together in a plane transverse to the axis of the envelope, concentric electrodes in the envelope including an anode, a tubular metallic lead perpendicular to said plane and extending through the upper section for supporting the anode, said upper envelope section being connected to the side walls of the tubular anode lead intermediate the ends of said lead, the lead providing a conductor for the anode and also communicating with the interior of the envelope to provide an exhaust tubulation, the outer end of the lead having its side walls compressed together to close the tubulation, and means on the lower envelope section for supporting others of said electrodes.

12. A tetrode' comprising an envelope having upper and lower sections joined together in a plane transverse to the envelope, concentric electrodes in the envelope including an anode and cathode and control grid and screen grid, a tubular metallic lead perpendicular to said plane and extending through the upper section for supporting the anode, said upper envelope section being connected to the side walls of the tubular anode lead intermediate the ends of said lead, the lead providing a conductor for the anode and also communicating with the interior of the envelope to provide an exhaust tubulation, the outer end of the lead having its side walls compressed together to close the tubulation, and means on the lower envelope section for supporting the cathode and control grid and screen grid.

DONALD F. DRIESCHMAN. HUBERT H. EAVES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Dorgelg Aug. 9, 1949